[Bldg-sim] Wind driven rain data

Joe Huang yjhuang at whiteboxtechnologies.com
Thu Jul 19 10:50:37 PDT 2018


Roel,

I have the following concerns about the approach you seem to be taking 
to define terrain-parameters for wind-driven rain:

(1) you are still basing your investigation on a rather simplistic model 
to derive wind-driven rain from the reported rain fall and wind speed, 
i.e., do you know how reliable is that model?

(2) for these types of correlations, you might want to use wind speeds 
at a much finer time resolution, since what's reported at the standard 
weather stations are random snapshots at an hourly or half-hourly time 
step.  You could consider using data from Personal Weather Stations 
(PWS), that are typically at the 5 minute interval and many also have an 
additional channel for gusts.  Such weather data, i.e., 5-minute data in 
urban or suburban areas, are currently available for tens of thousands 
of PWS, especially in North America and the UK, on web sites such as 
Weather Underground (www.wunderground.com). One caveat would be to know 
the placement of the PWS, which tend to be on rooftops (the problem is 
worse for official weather stations that are supposed to be at 10 m 
above the ground).   If you're interested in the WU weather data, let me 
know via e-mail.

I would not recommend using New York Central Park, or at least you 
should compare the results to that from some other place that's less 
atypical.   The Central Park  weather station  is located at the 
Belvedere (see attached map), which is an isolated building in the 
middle of a large urban park that is in turn surrounded by tall 
buildings and adjacent to some of the tallest buildings in the world.

Yes, I'm aware that the terminal velocity of raindrops varies with their 
size.  However, I ignored that factor because any error due to using a 
constant value would be small compared to all the other assumptions of 
the model and besides, I don't think raindrop size is recorded in any 
weather data.

Joe

On 7/19/2018 7:30 AM, Roel Tersteeg wrote:
>
> Dear Joe, Julien,
>
> Thank you for the extensive replies and your suggestions.
>
> The rainfall above an area is not very different between airfield and 
> urban areas, but due to the buildings and trees that may shelter 
> locations in build-up areas this can cause lower rainfall in those 
> locations. As you mentioned the wind will be altered in a more 
> significant way. One thing I would like to do is actually (re)define 
> ‘terrain parameters’ for wind driven rain. A single number, such as in 
> your example, hides the actual uncertainty behind that number. And for 
> that I would like to find measured data, the location of which doesn’t 
> matter that much.
>
> The usage of weather stations for the purpose I am looking for is 
> usually not an option as the location of weather stations is such that 
> buildings and trees around the site don’t have an effect on the 
> measurements (typically > 100 m around the site free of obstructions). 
> For the model I am trying to build, the (uncertainty in the) effect of 
> trees and buildings on rain and wind is exactly what I try to model. 
> If you know of weather stations on such sites, I would be grateful if 
> you could help me with that. I will also have a look at the weather 
> stations in central park and see if they can help me.
>
> As for the calculation presented, there are several methods (e.g. 
> ISO15927, ASHRAE standard 55) and they mostly have the form of 
> Rainfall*Wind_speed*cos(Wind_direction-Wall_normal), with possibly 
> some factors. There is a bit more explanation in Climatological note 3 
> from Met Eireann, from which note 13 is an update, how they calculated 
> the map.
>
> As a site-note: the velocity of raindrops is dependent on the size of 
> the droplet with larger drops having a higher speed (terminal 
> velocity) that smaller ones.
>
> Roel Tersteeg MSc
>
> PhD-student
>
> Building Energy Research Group
>
> School of Architecture, Building and Civil Engineering
>
> Loughborough University
>
> T: +44 77 56 10 90 54
>
> E: R.M.Tersteeg at lboro.ac.uk <mailto:R.M.Tersteeg at lboro.ac.uk>
>
> *From:*Julien Marrec <julien.marrec at gmail.com>
> *Sent:* 19 July 2018 13:26
> *To:* Joe Huang <yjhuang at whiteboxtechnologies.com>
> *Cc:* Roel Tersteeg <R.M.Tersteeg at lboro.ac.uk>; Luis Miguel Blanes 
> Restoy <lmblanes at gmail.com>; bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] Wind driven rain data
>
> Hello,
>
> FYI, I can think of at least one location where you'd find probably 
> good quality weather data in a *_big _urban center and not at an 
> airport: Central Park, New York City, USA*, though it's in a quite 
> large park but there are tall buildings all around it, see map 
> <https://www.google.com/maps/place/40%C2%B046%2744.4%22N+73%C2%B058%2708.4%22W/@40.7787947,-73.9765413,15.5z/data=%214m5%213m4%211s0x0:0x0%218m2%213d40.779%214d-73.969>.
>
> Note that in NOAA there's a weird thing going on where you have 4 
> stations with different operating dates, one did 1943 to 2010, another 
> 2010 to 2012 or so, and another started after that (I know I said 
> there are four: one did 17 days in august 2010 but overlapped another 
> running one). Here are the USAF-WBAN codes for the two most interesting:
>
> 725053-94728 #CENTRAL PARK (2012 to today)
>
> 725060-94728 #NEW YORK CENTRAL PARK (2010 to 2012)
>
> This data is free and can be accessed at NOAA's ISD (see here 
> <https://www.ncdc.noaa.gov/isd/data-access>)
>
> I looked at France's stations in the NOAA database too, since I have a 
> better clue of where things actually are, and it seems that there are 
> a bunch that aren't at an airport, but there are all in seaside towns, 
> so that is probably not what you're looking for...
>
> Here are some stations you'll perhaps want to look at, I'm including 
> the three airports around central park too if you want to compare the 
> data. Don't mind the fact that the 'END" date is last year, I just 
> haven't refreshed this file since September 2017
>
> USAF
>
> 	
>
> WBAN
>
> 	
>
> STATION NAME
>
> 	
>
> CTRY
>
> 	
>
> STATE
>
> 	
>
> ICAO
>
> 	
>
> LAT
>
> 	
>
> LON
>
> 	
>
> ELEV(M)
>
> 	
>
> BEGIN
>
> 	
>
> END
>
> 	
>
> KEEP
>
> 70020
>
> 	
>
> 99999
>
> 	
>
> BOULOGNE
>
> 	
>
> FR
>
> 	
> 	
> 	
>
> 50.733
>
> 	
>
> 1.6
>
> 	
>
> 74
>
> 	
>
> 19730101
>
> 	
>
> 20170902
>
> 	
>
> YES
>
> 72000
>
> 	
>
> 99999
>
> 	
>
> PENMARCH
>
> 	
>
> FR
>
> 	
> 	
> 	
>
> 47.8
>
> 	
>
> -4.367
>
> 	
>
> 19
>
> 	
>
> 19360102
>
> 	
>
> 20170902
>
> 	
>
> YES
>
> 73150
>
> 	
>
> 99999
>
> 	
>
> LA ROCHELLE
>
> 	
>
> FR
>
> 	
> 	
> 	
>
> 46.15
>
> 	
>
> -1.15
>
> 	
>
> 10
>
> 	
>
> 19290801
>
> 	
>
> 20170902
>
> 	
>
> YES
>
> 76410
>
> 	
>
> 99999
>
> 	
>
> SETE
>
> 	
>
> FR
>
> 	
> 	
> 	
>
> 43.4
>
> 	
>
> 3.7
>
> 	
>
> 81
>
> 	
>
> 19360615
>
> 	
>
> 20170902
>
> 	
>
> YES
>
> 76950
>
> 	
>
> 99999
>
> 	
>
> CAP FERRAT
>
> 	
>
> FR
>
> 	
> 	
> 	
>
> 43.683
>
> 	
>
> 7.333
>
> 	
>
> 144
>
> 	
>
> 19730101
>
> 	
>
> 20100412
>
> 	
>
> YES
>
> 725030
>
> 	
>
> 14732
>
> 	
>
> LA GUARDIA AIRPORT
>
> 	
>
> US
>
> 	
>
> NY
>
> 	
>
> KLGA
>
> 	
>
> 40.779
>
> 	
>
> -73.88
>
> 	
>
> 3.4
>
> 	
>
> 19730101
>
> 	
>
> 20170904
>
> 	
>
> YES
>
> 725033
>
> 	
>
> 94728
>
> 	
>
> NYC CENTRAL PARK
>
> 	
>
> US
>
> 	
>
> NY
>
> 	
>
> KNYC
>
> 	
>
> 40.779
>
> 	
>
> -73.969
>
> 	
>
> 47.5
>
> 	
>
> 19431201
>
> 	
>
> 20100731
>
> 	
>
> YES
>
> 725033
>
> 	
>
> 99999
>
> 	
>
> NEW YORK CITY  CENTRAL PARK
>
> 	
>
> US
>
> 	
>
> NY
>
> 	
> 	
>
> 40.767
>
> 	
>
> -73.983
>
> 	
>
> 27
>
> 	
>
> 20100801
>
> 	
>
> 20100817
>
> 	
>
> YES
>
> 725053
>
> 	
>
> 94728
>
> 	
>
> *CENTRAL PARK*
>
> 	
>
> US
>
> 	
>
> NY
>
> 	
>
> KNYC
>
> 	
>
> 40.779
>
> 	
>
> -73.969
>
> 	
>
> 42.7
>
> 	
>
> 20120801
>
> 	
>
> 20170904
>
> 	
>
> YES
>
> 725060
>
> 	
>
> 94728
>
> 	
>
> *NEW YORK CENTRAL PARK*
>
> 	
>
> US
>
> 	
>
> NY
>
> 	
>
> KNYC
>
> 	
>
> 40.779
>
> 	
>
> -73.969
>
> 	
>
> 47.5
>
> 	
>
> 20100801
>
> 	
>
> 20120801
>
> 	
>
> YES
>
> 744860
>
> 	
>
> 94789
>
> 	
>
> JOHN F KENNEDY INTERNATIONAL AIRPORT
>
> 	
>
> US
>
> 	
>
> NY
>
> 	
>
> KJFK
>
> 	
>
> 40.639
>
> 	
>
> -73.762
>
> 	
>
> 3.4
>
> 	
>
> 19730101
>
> 	
>
> 20170904
>
> 	
>
> YES
>
> Best,
>
> Julien
>
>
> --
> Julien Marrec, EBCP, BPI MFBA
> Owner at EffiBEM <http://www.effibem.com>
> T: +33 6 95 14 42 13
>
> LinkedIn (en <https://www.linkedin.com/in/julienmarrec>) /| /(fr 
> <https://fr.linkedin.com/in/julienmarrec/fr>) :
>
> 2018-07-19 3:55 GMT+02:00 Joe Huang via Bldg-sim 
> <bldg-sim at lists.onebuilding.org <mailto:bldg-sim at lists.onebuilding.org>>:
>
>     Roel,
>
>     I'm not an expert in this field of liquid precipitation, but here
>     are my thoughts in response to your comments:
>
>     1) I'm not aware of drastic differences in rainfall between the
>     airport and more urban areas of a city. However, there are
>     noticeable differences in wind speeds for which, in the absence of
>     measured data, are accounted for in building energy modeling by
>     TERRAIN-PARAMETERs dependent on the general site description,
>     e.g., 1.00 for flat terrain such as an airport, 0.85 for rural, 
>     0.67 for urban or forest, and 0.47 for urban centers with tall
>     building, and the height difference between the measured data and
>     the site.  if you're having difficulty in finding either measured
>     wind speed or driving rain data (good luck!), I would suggest you
>     just use the airport data and adjust that with a Terrain Parameter.
>
>     2) If you insist on getting rain and wind speed data for a
>     suburban location, I'm sure those can be found among the 8,000+
>     weather stations for which I have hourly weather data, but the
>     locations would be anywhere in the world.  Do you care where is
>     the location?
>
>     3) The Met Eirerann paper describes a driving rain index, but does
>     not provide the equation.  In thinking about it again (note that
>     I've only thought about this after reading your original query), I
>     think a plausible approach would be:
>
>        a. find the approximate downward velocity of falling rain (a
>     quick web search for "How fast do raindrops fall" gave the answer
>     of 10 m/sec)
>
>        b. divide that by the (adjusted) wind speed to get the fraction
>     that would fall on a vertical surface, i.e., driving rain.
>
>        c. multiply the "driving rain fraction" by the reported rain
>     fall to get the amount of driving rain.
>
>        c. use the wind direction to apportion the driving rain by the
>     wall orientation.
>
>     It's still not clear to me what is the primary motivation for your
>     investigation.  Is it to determine the amount of driving rain at a
>     particular location or weather file?  to validate the method to
>     calculate driving rain?  Or to just get a handle on how much
>     driving rain is there ?
>
>     Joe
>
>     Joe Huang
>
>     White Box Technologies, Inc.
>
>     346 Rheem Blvd., Suite 205A
>
>     Moraga CA 94556
>
>     yjhuang at whiteboxtechnologies.com
>     <mailto:yjhuang at whiteboxtechnologies.com>
>
>     http://weather.whiteboxtechnologies.com  for simulation-ready weather data
>
>     (o) (925)388-0265
>
>     (c) (510)928-2683
>
>     "building energy simulations at your fingertips"
>
>     On 7/18/2018 5:43 AM, Roel Tersteeg wrote:
>
>         Dear Joe and Luis,
>
>         Thank you for your replies to my question and apologies for my
>         very late reply to you both. Unfortunately the data from
>         official, synoptic weather stations is airfield data and thus
>         not applicable to my situation as there is no difference in
>         microclimate (no changes in wind or rainfall due to
>         surrounding building). The same goes for the Met Eireann
>         information (if of interest, the Climatological notes 13 and 3
>         about wind driven rain can also be found and downloaded here
>         as well:
>         https://www.met.ie/education/publications/climatological-notes)
>
>         I am looking specific for wind driven rain data, or indeed
>         combined wind and precipitation data that can be converted to
>         wind driven rain, for different (sub)urban settings. The
>         suggestion for looking at ‘personal weather stations’ is very
>         interesting, although this has the issue of uncertainty about
>         the quality of the measurements.
>
>         Kind regards,
>
>         Roel
>
>         *From:*Luis Miguel Blanes Restoy <lmblanes at gmail.com>
>         <mailto:lmblanes at gmail.com>
>         *Sent:* 06 July 2018 14:34
>         *To:* Joe Huang <yjhuang at whiteboxtechnologies.com>
>         <mailto:yjhuang at whiteboxtechnologies.com>
>         *Cc:* bldg-sim at lists.onebuilding.org
>         <mailto:bldg-sim at lists.onebuilding.org>
>         *Subject:* Re: [Bldg-sim] Wind driven rain data
>
>         Joe
>
>         Try this link
>
>         https://es.scribd.com/document/346851908/MET-Driving-Rain-Index-IRELAND#close_user_settings_menu
>
>         Regards
>
>         Luis
>
>         On Thu 5 Jul 2018, 04:28 Joe Huang,
>         <yjhuang at whiteboxtechnologies.com
>         <mailto:yjhuang at whiteboxtechnologies.com>> wrote:
>
>             Luis,
>
>             Thanks for the tip.  I went to the link, which by the way
>             is for the Irish Meteorological Service,  and read that it
>             said, "The amount of rain received by a wall correlates
>             fairly well with the product of rainfall and the component
>             of the wind speed normal to the wall. This led Lacy and
>             Shellard to propose the product of the mean annual
>             rainfall and the mean annual wind speed as a driving rain
>             index which is proportional to the total rainfall driven
>             in one year on to a vertical surface always facing the
>             wind", which is functionally quite close to what I was
>             envisioning, i.e., WDR = LP * f(wspd, wdir),  where LP is
>             Liquid Precipitation or Rainfall. However, when I clicked
>             on the link to the actual paper cited,  the Meteireann web
>             site responded that  "404: Page not found".  Therefore, I
>             still don't know the function that converts LP or rainfall
>             to WDR.
>
>             Joe
>
>             Joe Huang
>
>             White Box Technologies, Inc.
>
>             346 Rheem Blvd., Suite 205A
>
>             Moraga CA 94556
>
>             yjhuang at whiteboxtechnologies.com
>             <mailto:yjhuang at whiteboxtechnologies.com>
>
>             http://weather.whiteboxtechnologies.com  for simulation-ready weather data
>
>             (o) (925)388-0265
>
>             (c) (510)928-2683
>
>             "building energy simulations at your fingertips"
>
>             On 7/4/2018 2:30 PM, Luis Miguel Blanes Restoy wrote:
>
>                 Hi Roel and Joe
>
>                 Did you look at available data from Met Eireann? There
>                 is a paper regarding WDR index calculation method that
>                 may be of your interest. See below link.
>
>                 https://www.met.ie/climate/what-we-measure/rainfall#
>                 <https://www.met.ie/climate/what-we-measure/rainfall>
>
>                 Regards
>
>                 Luis
>
>                 On Wed 4 Jul 2018, 22:12 Joe Huang via Bldg-sim,
>                 <bldg-sim at lists.onebuilding.org
>                 <mailto:bldg-sim at lists.onebuilding.org>> wrote:
>
>                     What is your definition for Wind-driven Rain?
>                     Practically all weather station reports, including
>                     official stations available in NOAA's ISD as well
>                     as unofficial "Personal Weather Stations" hosted
>                     on WeatherUnderground, contain information on
>                     liquid precipitation (LP), wind speed, and wind
>                     direction. Can the WDR be calculated from these
>                     standard parameters, maybe as the LP * f(wspd, wdir) ?
>
>                     Joe
>
>                     On 7/4/2018 3:52 AM, Roel Tersteeg via Bldg-sim wrote:
>
>                         Dear all,
>
>                         For the verification of a model to estimate
>                         wind driven rain (WDR) I would like to use WDR
>                         data from different microclimates (rural,
>                         (sub)urban). I have access to several data
>                         sets of free field or airfield WDR
>                         measurements from different locations and the
>                         results from a measurement campaign in
>                         Vancouver. To better evaluate the model I
>                         would like to use measured data from one or
>                         more locations with different microclimates,
>                         not being free field or airfield sites.
>
>                         My question is if someone knows if
>                         measurements are available of wind driven rain
>                         in one or more microclimates?
>
>                         Kind regards,
>
>                         Roel Tersteeg MSc
>
>                         PhD-student
>
>                         Building Energy Research Group
>
>                         School of Architecture, Building and Civil
>                         Engineering
>
>                         Loughborough University
>
>                         T: +44 77 56 10 90 54
>
>                         E: R.M.Tersteeg at lboro.ac.uk
>                         <mailto:R.M.Tersteeg at lboro.ac.uk>
>
>                     _______________________________________________
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